Compatible Coils for Use with HotSpark® Ignition
Applies to Hot-Spark 3-Series (red) ignition kits
Coil Warning: DO NOT use a low-resistance or an HEI-style coil. 4-Cylinder: Use a coil that has resistance in the primary circuit of at least 3.0 Ohms (Ω). 6- and 8-Cylinder: Must be used with a coil that has resistance in the primary circuit of at least 1.5 Ω. Using a coil with insufficient primary resistance can cause the ignition module to overheat and misfire until it cools down again, or fail prematurely, which will void the Hot-Spark ignition warranty.
DO NOT reverse the polarity of the red and black wires - it will destroy the ignition module (and void its warranty)! The Hot-Spark module’s red wire connects to positive ( + or 15 on Bosch coil). The black wire connects to negative ( - or 1 on Bosch coil). Remove the condenser and its wire from vehicle. All other wires are connected to the coil in their original places. This module is designed for 12V negative ground applications only.
Make sure that the ignition wires have plenty of slack inside the distributor and are not rubbing on any moving parts. If you need to extend the length of the ignition wires, use 18- or 20-gauge (AWG) wire. Crimp tightly or solder (best) and insulate all connections.
The BERU Germany Blue Coil has 3.3 Ω primary resistance. Ideal for 4- and 6-cylinder applications.
The HotSpark® HS17HEC high-energy coil (epoxy-filled) has 1.7 Ω primary resistance (for 6- and 8-cylinder applications only).
The following 12-volt Bosch® coils should be compatible with the Hot-Spark electronic ignition module (4-cylinder):
0 221 119 021 (Bosch Black coil)
0 221 119 020 (Bosch Black coil) (VW 022 905 115C)
0 221 119 027 (Bosch Blue coil) (VW 043 905 115C)
9 220 081 039 (Brazil)
9 220 081 054 (Brazil)
9 220 081 083 (00 012) (Bosch Blue coil)
0 439 051 15C (00012) (Bosch Silver Coil)
The Bosch coils above should have a primary winding with 3.0 to 3.3 Ω resistance. Bosch coils are made in a number of countries, with varying amounts of primary and secondary resistance. It's best to check the coil's primary resistance with an Ohmmeter (a digital multi meter in the 200 Ω mode). Install a 1.4 Ω or so external ballast resistor (HS14BR) between the ignition switch (+12-Volt power source) and the coil's + terminal, if the coil's primary resistance is questionable or borderline.
Bosch 0 221 119 030 (Bosch Red Coil, Brazil) 1.6 Ω to 1.8 Ω primary resistance (OK for 6- or 8-cylinder ignition kits, not enough primary resistance for 4-cylinder ignition kits).
BERU Germany Blue Coil: 3.3 Ω primary resistance
Lucas® Coil Primary Resistance:
DLB102 1.5 Ω (oil-filled)
DLB110 1.5 Ω (oil-filled)
DLB105 3.0 Ω (oil-filled)
DLB101 3.0 Ω (oil-filled)
Flame-Thrower® (made in China) Coil Primary Resistance:
40001 1.5 Ω (oil-filled)
40011 1.5 Ω (oil-filled)
40111 1.5 Ω (epoxy-filled)
40501 3.0 Ω (oil-filled)
40511 3.0 Ω (oil-filled)
40611 3.0 Ω (epoxy-filled)
Do not use any other Flame-Thrower®
coil, as it won't have enough primary resistance, allowing too much amperage to
flow to the ignition module, destroying the module or shortening its life.
LU800 3.3 Ω primary, 8.3K Ω secondary resistance (oil-filled)
Duralast® (Autozone®) LU800 3.3 Ω primary, 8.3K Ω secondary resistance (oil-filled)
Epoxy-filled coils can be mounted
in any position and are able to withstand more vibration and shock than
Measuring Coil Resistance: 4-Cylinder: Coil must have a minimum of 3.0 Ohms primary resistance. 6- and 8-cylinder: Coil must have a minimum of 1.5 Ohms primary resistance. To measure primary resistance: Label and remove all wires to coil ( + or - ). Using a common digital multimeter in the 200 Ω mode, cross the red and black leads of the Ohmmeter. Allow a few seconds for the reading to settle and write down the reading.
Still in the 200 Ohm mode, measure between coil’s + and - terminals. Allow a few
seconds for the reading to settle, until it stabilizes. Subtract the previous
reading, taken with the leads crossed, to compensate for multimeter’s inherent
resistance. Do not use a low-resistance coil, such as the MSD or Accel coil;
they don’t have enough primary resistance for this application.
Using a coil with too little primary resistance can cause
the ignition module to overheat and misfire until it cools down again or fails,
voiding the warranty.
Check the voltage reading at the coil's + terminal, engine running, at 2,500+ RPM. If the voltage measures more than +14.0 volts, you'll need to replace the voltage regulator, install a coil with 3.0 Ohms or more internal primary resistance or install a 1.4 Ohm external ballast resistor between the ignition switch and the coil's + terminal. Charging system voltage of 13.6 volts or so is plenty.
For best performance, the coil should also have 7,000 (7K) Ohms or more secondary resistance (measured from coil’s + or – terminal to center high tension terminal, in the 20K Ω mode of the Ohmmeter).
Do not use a coil designed to be used with an external ballast resistor. These coils usually have little-to-no internal primary resistance.
External Ballast Resistor:
6- and 8-Cylinder: If your coil’s primary resistance measures less than 1.5 Ω,
you’ll need to replace the coil with one of 1.7 Ω or more primary resistance or
to install a 1.4+ Ω external ballast resistor between the ignition switch and
the coil’s positive terminal, increasing the total primary resistance to 1.7 Ω
or more. 4-Cylinder: Either use a coil with 3.0 Ω or more primary
resistance or a coil with 1.6 Ω or more primary resistance and an external
ballast resistor with 1.4 Ω or more resistance, wired between the ignition
switch and the coil's + terminal.
With the ignition switch on and engine not running, the voltage, measured at the coil’s positive terminal, after installing the ballast resistor, should be about the same as battery voltage, or somewhere around 12.5 volts for proper operation of the Hot-Spark ignition module and the coil.
Check Charging System Voltage:
Begin with a fully-charged battery. With the ignition switch in the ON position and the engine not running, measure the voltage at the coil's + terminal. With the voltmeter in the 20-volt setting, touch the black voltmeter lead to engine ground and the red lead to the coil's + terminal. The voltmeter should read between +11 and +13.9 volts. If the voltage reading is less than 10 volts, there is probably a resistor wire or ceramic external ballast resistor wired between the ignition switch and the coil.
If your vehicle’s charging system produces more than 14.0 volts at high RPM
(about 2,500+ RPM, measured at coil's positive terminal), we recommend installing
an external ballast resistor with about 1.0 to 1.4 Ω resistance, wired between the
from the ignition switch (+12-volt power supply) and the coil’s positive terminal.
The extra primary resistance helps to keep the coil and ignition module cool,
prolonging their lives and ensuring trouble-free operation. The ballast resistor
is usually mounted on the firewall or on or near the coil.
If the charging system voltage, measured at the coil's positive terminal, is more than 14.0 volts at 3,000+ RPM, the voltage regulator likely needs replacing. Too much voltage can damage the coil, ignition module and other electronic components. Maximum charging system voltage of 13.6 volts or so is plenty.
Calculating Amperage to the Distributor
Some vehicles have overactive electrical charging systems, sending 14.0 volts or more to the coil's + terminal, shortening the life of the points, coil or electronic ignition module. If peak charging system voltage exceeds 14.0 volts at 3,000+ RPM, the voltage regulator may need replacing. A modern, solid-state voltage regulator is a big improvement over an older mechanical voltage regulator. To test your ignition system’s compatibility with the Hot-Spark ignition module, you’ll need to run a couple of tests:
1. Determine the voltage leading to the coil’s positive terminal
from the ignition switch and if a resistor wire is present: Begin with a fully
charged battery. Start the engine and let it idle. Connect the black lead of a
voltmeter to engine ground. Connect the voltmeter’s red lead to the positive ( +
or 15) terminal of the coil and the voltmeter's black lead to engine ground
(earth). With the voltmeter in the DCV 20 mode, note the
voltage reading. If the voltmeter reads +12 volts or more, there’s little or no
resistance in the wire going from the ignition switch to the positive terminal
of the coil. If the wire leading from the ignition switch to the coil’s positive
terminal is a resistor wire, the voltmeter will typically read +6 to +10 volts DC.
Now, start and rev the engine until the voltage stops increasing (usually about 3,000
RPM). Write down the voltage reading.
2. Next, measure the resistance of the coil’s primary winding:
Label and disconnect all wires going to the coil. Make a note of to which
terminal (+ or -) each wire goes. Using an Ohmmeter in the 200 Ohm (Ω) mode,
touch the black lead to the coil’s negative terminal and touch the red lead
to the coil’s positive terminal. The Ohmmeter will display the resistance of the
coil’s primary winding. Allow a few seconds for the resistance reading to settle
downward until it stabilizes. Write down the coil’s primary resistance reading
Ohmmeter Calibration: When the Ohmmeter’s red and black leads are connected to
each other, the reading should be 0.00 or very close to zero. If, though, for
example, with both Ohmmeter leads shorted together, the reading is 0.5 Ω, you’ll
need to subtract 0.5 Ω from the reading you get when measuring the coil’s
primary resistance. For example, if the coil’s primary resistance reading is 3.5 Ω, but
when the Ohmmeter leads are shorted together the reading is 0.5 Ω, then the
coil’s primary resistance is 3.0 Ω: 3.5 Ω - 0.5 Ω = 3.0 Ω. This calibration
procedure applies only to resistance measurements made in the 200 Ω mode of a
digital Ohmmeter. The inherent resistance of the leads is negligible in higher Ω
modes of the Ohmmeter. If you’re using an analog Ohmmeter, touch the leads
together while setting the needle on zero before measuring resistance.
3. Now, divide the voltage reading from Step1 by the coil’s
primary resistance, in Ω, from Step 2. For example, if the voltage is 12.75
volts and the coil’s primary resistance is 3.3 Ω, the current running through
the points or Hot-Spark module would be 3.86 amps:
Example: 12.75 volts / 3.3 Ω = 3.86 amps (OK)
Example: 14.3 volts / 3.3 Ω = 4.33 amps (too much current for a 4-cylinder electronic ignition module)
More than 4.0 amps of current is too much for the ignition
module when used in a 4-cylinder distributor. More than 4.0 amps can cause the
module and coil to run too hot and the module and/or coil to possibly misfire or
and/or fail. 6- and 8-cylinder ignition kits can be used with an ignition coil that has
a minimum of 1.5 Ω primary resistance.
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